Analysis and design of a leaky-wave EMC dipole array

An analysis of an electromagnetically coupled (EMC) dipole array is presented, in which a microstrip line is coupled to an infinite periodic linear array of microstrip dipoles, arranged perpendicular to the line. The spectral-domain immittance method is used to obtain the periodic Green's function for the two-layered structure, and the method of moments with a Galerkin testing procedure is then used to enforce the electric field integral equation (EFIE) on the line and the dipole within a unit cell of the structure to obtain the determinantal equation for the unknown leaky-wave propagation constant. One of the interesting features of this analysis is the path of integration in the complex plane used to compute the moment method reactions, which must be partly on the improper sheet for the m=-1 space harmonic when it radiates in the forward direction. Measured radiation patterns for a 10-element EMC dipole array are presented and compared with the corresponding theoretical ones     

Corporate feed design for microstrip arrays

A design technique for an embedded microstrip corporate feed is presented. The aim of the design is to shape each corporate feed junction to achieve a tapered and in-phase output current distribution. From this, a Dolph-Chebyshev array sum pattern may be constructed. In the experiments, the designed corporate feed is used to excite a five-element equispaced linear array of overlay microstrip dipoles. It is found both theoretically and experimentally that a 20-dB Dolph-Chebyshev broadside sum pattern can be synthesized in the H-plane at 8.5 GHz. Mutual coupling among the dipoles is included in this analysis. The pattern degradation due to manufacturing tolerances on the alignment between the feed network and the dipole array is discussed     

Mutual coupling between microstrip dipoles in multielement arrays

An analytical method for evaluating mutual coupling in multielement microstrip arrays is discussed. The elements of the array are strip dipoles covered by an overlayer and excited by microstrip lines embedded in the substrate. In addition, two different ways of excitation are considered to evaluate the effect of the feeding lines on the coupling between the dipoles. Throughout the analysis, the transmission line and dipole widths are taken to be a fraction of the free-space wavelength, so that the longitudinal current component is the dominant contributor to the characteristics of the array. Under this assumption, the transverse component of the current is neglected without introducing appreciable error. The current distribution along the longitudinal direction is evaluated by solving an appropriate integral equation using Galerkin's method with piecewise continuous sinusoidal functions. All possible interactions between the currents on the feeding transmission lines and dipoles are included. Using the computed current distribution, transmission-line theory is applied on the feeding microstrip lines to evaluate self- and mutual impedances as well as scattering coefficients at chosen reference planes     

The design of microstrip dipole arrays including mutual coupling, part II: Experiment

Experiments are described from which determination can be made of the self and mutual impedance for microstrip dipoles and of the backscattering relation involving the radiating current. Functional representations of these sources of input data then permits the design of planar microstrip dipole arrays, including the effects of mutual coupling. The design, construction, and performance of a typical array are described. Agreement between theory and experiment is good.     

A quasi-periodic design procedure for a traveling-wave array ofdipoles

A simple iterative design procedure is given for a traveling-wave array of dipole elements fed in a shunt configuration by a meandering transmission line. The design procedure is based on a quasi-periodic analysis of the loaded line, which assumes a Bloch wave propagation on the structure. A design procedure is formulated for the cases of constant attenuation and tapered attenuation on the line. A ten-element array of vertical monopoles fed by a meandering stripline is used to illustrate the design technique. Results show that the design procedure based on power into the dipoles gives good agreement with one based on actual dipole currents if a certain assumption is used. It is important, however, to account for mutual coupling in the design procedure in order to obtain accurate patterns, especially for low sidelobe designs     

Scanning characteristics of infinite arrays of printed antennasubarrays

The analysis and scanning characteristics of several different types of infinite arrays composed of subarrayed printed dipole and microstrip patch elements are presented. The analysis is based on full-wave moment method theory, and includes mutual coupling between elements in the subarray as well as between subarrays. The effect of subarraying on scan blindness is demonstrated for arrays using two-element subarrays of printed dipoles and microstrip patches. Results are also given for the amount of power radiated in grating lobes. The effect of a subarray composed of one driven element and one parasitic element, and the use of a four-element synchronous subarray of microstrip patches to generate circular polarization are also considered. Data are given for impedance mismatch, power radiated into grating lobes, and the axial ratio; both square and rectangular patches area considered. Results are also shown for an infinite array of seven-element hexagonal subarrays of printed dipoles, and it is found that the large spacing between subarrays leads to a limited scan range     

Analysis and design of series-fed arrays of printed-dipolesproximity-coupled to a perpendicular microstripline

An analysis of a printed dipole element and a generalized configuration of a series-fed array of such elements, electromagnetically coupled to a covered microstripline running perpendicularly under it in a substrate-superstrate configuration, is presented. The solution is based on the principle of reciprocity and is formulated using a rigorous method of moments and full-wave spectral-domain Green's functions for multilayer dielectric substrates. The dipole excitation is characterized by an equivalent impedance, and can be controlled by suitably selecting the offset of the dipole from the feed line. Mutual coupling between dipoles is included. Using the results of the element analysis, a series-fed array prototype has been successfully designed, built, and tested in a standing-wave configuration; the design details are described, and measured performances are evaluated using the results of the array analysis. Mutual coupling effects are found to be not detrimental for this configuration, but can be severe for other nonstanding-wave configurations     

Synthesis of linear arrays of series fed proximity-coupled microstrip antennas

This paper presents a synthesis of linear standingwave arrays of microstrip antennas such as transverse dipoles, series-fed by a proximity coupled microstrip line. Each radiating element is characterized by its self-admittance and mutual coupling admittance. The self-admittance depends on geometrical parameters and on the nature of the substrate, while the mutual coupling admittance is related to the presence of the other radiating elements. These values are computed exactly using an integral equation technique combined with a two-port model of the element. The synthesis procedure is validated with measurements of the radiation pattern and a return loss of a 20-dipole array. The importance of mutual coupling in the design process is clearly demonstrated.     

Design of transversely fed EMC microstrip dipole arrays includingmutual coupling

Design techniques and procedures for microstrip dipole arrays transversely fed by proximity coupled microstrip lines are presented. Two design equations which include the effects of mutual coupling are developed, and the corresponding design curves are obtained by a rigorous integral equation solution. A seven-element standing wave linear array is designed to illustrate the developed design procedures. The design data are checked by a complete integral equation solution of the array, with good agreement. The measurements of radiation pattern and input impedance are found to be in good agreement with the design goal     

Infinite array of printed dipoles integrated with a printed stripgrating for suppression of cross-polar radiation. I. Rigorous analysis

A rigorous analysis of an infinite array of printed dipoles integrated with a covering layer of printed strip grating is presented. Such designs can be useful to achieve low to ultra-low levels of cross-polar radiation from printed antennas, which is otherwise difficult to obtain from standard printed antenna designs. The analysis rigorously accounts for coupling between the grating strips and the dipole array in a general multilayered environment. Various demonstrative and design results showing loading effects of the grating on scan and impedance characteristics of the array are presented. Some interesting fundamental effects of the grating on the cross-polarization level and scan-blindness behavior are discussed     

On the modeling of electromagnetically coupled microstrip antennas--The printed strip dipole

A generalized solution for a class of printed circuit antennas excited by a strip transmission line is presented. The strip transmission line may be embedded inside or printed on the substrate. As an example, microstrip dipoles electromagnetically coupled (Parasitically excited) to embedded strip transmission line have been analyzed accurately, and design graphs are provided for a specific substrate material. These graphs permit the establishment of a design procedure which yields the microstrip dipole length, overlap, offset, and substrate thickness with the goal of a desired input match for a given substrate material. The method accounts for conductor thickness and for arbitrary substrate parameter. Comparison with experiment shows excellent agreement.     

Dielectric cover effect on rectangular microstrip antenna array

A theoretical model to analyze a covered rectangular antenna with an arbitrary dielectric constant superstrate is developed. The antenna is simulated by the radiation of two magnetic dipoles located at the radiating edges of the patch. The Green's function of an elementary magnetic dipole in a superstrate-substrate structure, utilizing spectral-domain analysis, is formulated, and the surface-wave and radiation field are computed. An improved transmission line model, which considers the stored energy near the radiating edges and the external mutual coupling, is used to compute the input impedances and radiation efficiency. Design considerations on the superstrate thickness and its dielectric constant are discussed. Experimental data for a single element and a 4×4 microstrip array is presented to validate the theory     

多级微带/带状线混合馈电网络设计

提出了一种用于低副瓣雷达的印刷振子阵列天线的多级微带线/带状线混合馈电网络结构,具有集成度高、结构紧凑、重量轻等优点.并基于对各子网络散射矩阵的级联分析,获得了S波段中相对带宽为10%的1:48多级混合网络的良好的散射矩阵特性.测试结果表明了本文方法的有效性.     

Wideband microstrip array antenna with sidelobe cancellationchannels

An antenna array for wideband operation (up to 70%) is presented. The structure has low windloading area and consists of parallel printed circuit boards (PCB) with microstrip dipoles, feed network and metal fences placed between the PCBs. The low profile, low weight antenna array forms the main beam and three difference patterns for sidelobe cancellation. Experimental results are compared with calculations for both microstrip dipole and array     

Optimum element lengths for Yagi-Uda arrays

An analytical method is developed for the maximization of the directivity of a Yagi-Uda array by adjusting the lengths of the dipole elements. The effects of a finite dipole radius and the mutual coupling between the elements are taken into consideration. Currents in the array elements are approximated by three-term expansions with complex coefficients that convert the governing integral equations into matrix equations. Array directivity is maximized by a perturbation procedure that adjusts the lengths of all array elements simultaneously and that converges very rapidly. This method can be combined with the previously developed spacing-perturbation method to form a double-perturbation procedure and obtain a Yagi-Uda array of nonuniformly spaced elements of unequal lengths. which yields a maximum directivity.     

Considerations for millimeter wave printed antennas

Calculated data are presented on the performance of printed antenna elements on substrates which may be electrically thick, as would be the case for printed antennas at millimeter wave frequencies. Printed dipoles and microstrip patch antennas on polytetrafluoroethylene (PTFE), quartz, and gallium arsenide substrates are considered. Data are given for resonant length, resonant resistance, bandwidth, loss due to surface waves, loss due to dielectric heating, and mutual coupling. Also presented is an optimization procedure for maximizing or minimizing power launched into surface waves from a multielement printed antenna array. The data are calculated by a moment method solution.     

Basic blocks for high-frequency interconnects: theory andexperiment

Proximity-coupled open-end microstrip transitions in double-layer planar structures are investigated through the method of moments solution of integral equations. Two types of EMC (electromagnetically coupled) microstrip lines are considered, namely, collinear lines and transverse lines. It is found that these transitions are broadband and provide a wide range of coupling coefficients. The theoretical model for the transverse microstrip transitions is in good agreement with measurements     

Analysis of planar strip geometries in a substrate-superstrate configuration

A moment method procedure is used to analyze the behavior of several different configurations consisting of planar strips in a substrate-superstrate geometry. These include the microstrip transmission line, center-fed dipole, the mutual impedance between two dipoles, and the transmission-line coupled dipole. In each case some of the basic superstrate effects are discussed.     

Analysis of mutual coupling between a finite phased array ofdipoles and its feed network

The mutual coupling effects between a finite phased array of dipoles and its feed network are analyzed. The feed network is typically a corporate feed consisting of split-tee power dividers cascading to form a certain power distribution over the aperture. A simple iterative approach is used to solve the interaction between elements and feed. The radiation of a finite dipole array are first found for a given voltage excitation. These radiation impedances are then used as loads for the feed network, and the n+1 port network problem is analyzed. Due to the interaction between the feed network and dipoles, the antenna parameters such as mismatch, antenna pattern, and gain are all affected. These effects can be determined from the analysis of the network representation. Numerical results for a typical phased array with a corporate feed show that the resultant VSWR of the feed pattern degradation is due to the mutual coupling effects     

Microstrip dipoles on electrically thick substrates

Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed.